angiosperms characteristics
Characteristics of Angiosperms
This article provides a detailed overview of the characteristics of angiosperms that every budding botanist should know.
- Angiosperms are able to grow in a variety of habitats. They can grow as trees, shrubs, bushes, as well as herbs. These plants have diploid (2n) sporophytes. Angiosperms have a distinctive underground root, as well as aerial shoot system.
- Angiosperms have very well-developed conducting tissues. These tissues include the xylem and the phloem arranged in form of vascular bundles. The xylem contains vessels. Similarly, phloem consists of sieve tubes and companion cells.
- The vascular bundles of monocotyledons are arranged in stems, in a cross-section. The dicotyledons have vascular bundles organized in form of a ring. A pith for storage, as well as cortex for strength and structure are found in the stem tissues. Growth of stem tissues takes place due to a layer of cambium cells. The outer part of the stem tissues is covered with a layer of epidermis.
- The root system of angiosperms is also very complex. The roots also contain cortex, phloem, xylem, and epidermis. They have root hair that help in better absorption of water minerals from the soil. Absorption takes place by diffusion and active transport.
- The leaves carry out photosynthesis and are covered with a waxy cuticle to avoid water evaporation from leaves. There is absence of stomatal openings in the upper epidermis. This helps in prevention of excess transpiration. The stomatal openings are present in the lower epidermis.
- The flowers are one of the most differentiating features of angiosperms. They are the reproductive structures of angiosperms. The flower has a thalamus that is a short axis and four whorls of sporophylls arranged on the thalamus. The four whorls of floral leaves include calyx, corolla, androecium and gymnocium. The sepals, petals, stamens and carpels make up the whorls.
- The stamens produce pollen that helps in pollination when they reach the stigma. A pollen tube containing non-motile male gametes is produced after germination of a pollen grain. The pollen tube reaches the ovary through a style. Ovaries of an angiosperm contain a nucellus and two integuments containing a micropyle. Closed carpels that enclose the ovules help in prevention of self-fertilization.
- Prime features that distinguish angiosperms also include double, as well as triple fusion. This leads to formation of a zygote (2n) and triploid endosperm cell (3n). Endosperm cell produces endosperm and zygote develops into a sporophyte.
- Fertilization takes place by pollination, that includes insect pollination, wind pollination, etc. Endosperm is produced after fertilization and before the zygote undergoes its first division. The endosperm helps in providing nutrition to the developing embryo, as well as the seedlings. The fertilized ovule develops into seeds and then ripens into a fruit. The seeds are enclosed in the fruits and are dispersed by animals and humans who eat the fruit.